Friends raised the alarm soon after 10pm on Sunday night when the woman failed to surface.

Police divers with the help of lights from a helicopter searched the water and were joined by Scottish Fire & Rescue Service teams, but they were stood down 30 minutes after midnight.

Police Scotland’s Dive & Marine Unit was set to undertake further searches today.

Two teenagers have died in the quarry in the past three years in non-diving-related incidents that caused it to be fenced off, with warning signs erected and police patrols, but the site is said still to be popular with scuba-divers. Maximum depth is 11m.

*   Two male scuba-divers were being treated for possible decompression illness following rapid ascents from 20m in the North Sea yesterday morning (9 July).

The incident occurred about seven miles north of Hartlepool in Co Durham.

Humber Coastguard called out the Hartlepool RNLI lifeboats, which were on the scene within 20 minutes.

The men were taken to James Cook University Hospital in Middlesbrough.

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