https://www.dailypost.co.uk/news/north-wales-news/major-rescue-operation-launched-after-21260666

I presume they entered the top adit, and somehow fell into the pit - both of them apparantly.

Slightly more details emerging
https://www.bbc.co.uk/news/uk-wales-58143594

That adit looks like it'd benefit from a gate of some sort, but hopefully not completely sealed after this...

Hopefully the seriously injured one isn't too bad. They normally get flown to Stoke on Trent from around here for bad injuries.

RobinGriffiths said:

Hopefully the seriously injured one isn't too bad. They normally get flown to Stoke on Trent from around here for bad injuries.

Click to expand...

They hadn't ad'it then?

There is another thread about this in Wales forum, with different news articles linked

I think from the photos that this might be the adit where in 1971 an easy traverse above water was made more interesting by the presence of large amounts of barbed wire and rusty corrugated iron.

I prospected the area for nickel and ....err....there is not much nickel there.

Much more interesting are the Benallt mines, further up the hill. That must have a drainage adit. We descended to the 15 fathom back in the 90s, and it was bone dry. That needs a revisit.

This is the highest adit, down the hill from the mast. Despite appearance it is no more than a trial - about 3 metres long.

https://m.facebook.com/story.php?story_fbid=255327356403053&id=100057773705329
Abersoch coastguard FB with some details and a report by members of the affected party, quoted below

There are many old mine workings on the coast of Pen Ll?n but please do not be tempted to explore these extremely dangerous sites. Here?s a thank you message and a salutary warning of what can happen when things go badly wrong.
* * * * * * * * * * * * * * * * * * * * * * * *
Today we woke extremely grateful to all 6 emergency services that came to our rescue on a day of exploration that quickly turned in to a nightmare.

The reason for this post is to raise awareness of the dangers, show our immense gratitude and to help raise funds for these vital, and mostly voluntary services.

Yesterday, a fairly large group of us were at Porth Ysgo, enjoying the beach scenery & it?s picturesque waterfall.

Some of our party had previously explored a cave in the mountain side and they wanted to share their experiences with us.

Unfortunately, this led to a 19 yr old girl in our group, falling in to an old mine.
She was trapped in total for 3 long hours, another member of our party constantly reassured her that help was on its way, although initially she wasn?t responding, once her voice could be heard he kept her talking until the emergency services arrived.

Access was extremely difficult, meaning the various emergency services struggled to reach her.
The fact the space inside the cave was so tight, meant they couldn?t set up their safety equipment, despite using two different entry points to the cave.

Fortunately, the cave rescue team discovered another point of access further down the mountain, which meant they could reach her, use their vital equipment to assess her condition and bring her out to safety. She was then taken by air ambulance to Bangor hospital.

The incredible emergency services included two coastguard teams, ground and air, mountain rescue, cave rescue, air ambulance and the ground paramedics & critical care consultant to whom we express our sincere gratitude and we will be donating to each charitable cause.

Thankfully, the outcome is she has a broken arm & although she is badly battered and bruised, she will be ok. She has gone back to the hospital today for further x-rays on her hip.

Please use extreme caution when out exploring, we are, as a rule, a relatively cautious group, so it just shows that these freak accidents can happen to anyone and you never know if you, yourself, may need these amazing people to come to your aid.

Just to add the ?What 3 Words? app helped the emergency services find our exact location.

Stay safe everyone and donate if you can?..

The position of the stretcher inside would suggest they'd fallen from the hanging part of the fourth adit (it runs in to a blind but has a short, slightly downward sloping section to the left which is usually damp. This opens to the main stoped area with a 20foot or so drop. If walking fairly blindly along the tunnel using a poor light a person could fall down therwe but the article says two of them did and that seems very unlikley. There are no 'shafts' or 80 foot drops at Nant?
The next most likley place to fall would be into the opencast (which is fenced at ther surface but can be accessed easily down another short adit. They clearly didn't fall into that area based on the photos.
Numerous other places you could slip/fall but none liley to cause more than grazes/bruises.

My reading of the info was one fell, and the second stayed in to maintain contact but wasnt trapped / needing rescue as such. It would appear there was a lower adit leading to the casualty who luckily had only a broken arm and scrapes...

I know this will be controversial to some, but!
Is there a local group, with a good relationship with the landowner that could make the entrances safe?
I predict that the local council will be ordering bulldozers and concrete given half a chance! 

Agree with Wayland, controlled access is far better than a dumper truck of concrete in the hole.
Maybe the "bat habitat" card can be played?

The info says that there was a lower access  which means that the fall must have been from the hanging adit.
If that was blocked at the outside there would still be easy access to the rest of it (and that adit is of no particular interest to anyone and isn't used by bats)
The next most dangerous part is probably the opencast and the farmer has made that significantly worse by using it as a personal refuse site. If they sealed the adit entrance that leads to a lower edge of that it wouldn't be a significant loss or prevent someone who really wants to get in from doing so...again, it wouldn't affect bats

Blocking the adit may affect the bats as there need a current of air.

rhychydwr1 said:

Blocking the adit may affect the bats as there need a current of air.

Click to expand...

Those are not the only adits and, so far, bats (a handful of Lesser Horseshoe) are only in an unconnected area.

Had a recce yesterday, and despite two adits leading to drops within a short distance of the entrance, not a warning sign in sight. The only sign there is a No Fly Tipping on the fence around the open cast, rather amusingly, the Welsh version saying Dim Tipio Slei - No Sly Tipping!

Oh, and one of these has a geocache in an ammo box just inside, so that'll be attracting some traffic.