By Vanessa Buschschlüter
Attempts to rescue 10 men from a flooded mine in Mexico have been delayed after the water levels in three shafts rose suddenly on Sunday.
The miners became trapped on 3 August when a wall in a tunnel collapsed and water from an adjacent chamber gushed into the three shafts.
Officials say the water has to drop to a depth of 1.5m (5ft) to allow rescuers to enter the shafts safely.
But on Sunday, it suddenly rose again to more than 20m.
The governor of Coahuila state, where the coal mine is located, said the water was probably flowing into the shafts from a nearby disused mine. Governor Miguel Riquelme said engineers were trying to find the source of the leak so they can block it.
More than 200 million litres have been pumped from the shafts so far, but the rescue work has been hampered by a number of setbacks.
Last week, a special underwater drone carrying a camera was lowered into one of the shafts.
Relatives of the miners had hoped the drone would provide them with long-awaited news on their loved ones, from whom there has been no sign of life since the accident 12 days ago.
But the drone failed to reach the depth at which the miners are believed to have become trapped.
"There are a great number of solid obstacles and turbulence in the water, which make visibility very limited," a statement said.
"These are not conditions in which we can send in search and rescue teams."
Relatives of the 10 trapped miners again expressed frustration and anger at the slow pace of the rescue effort and at what they said was a lack of communication.
"We want them (authorities) to tell us what is happening: if they have identified the places where water is coming through and why," a member of miner Sergio Cruz's family told Reuters news agency.
Priests in the area have been saying prayers for the miners' rescue.
This video can not be played
Watch: Rescue mission to free ten Mexican miners
Frustration of trapped miners' relatives grows
Colombia rescuers 'won't give up' search for miners
Iran blames Rushdie and supporters for stabbing
Lyse Doucet: From Kabul and beyond, a year of Taliban rule
How much aid is reaching Afghanistan? Your questions answered
Forty metres above the forest, searching for smoke
The DIY tech that made Gandhi's voice heard
Why was British India partitioned 75 years ago?
How 40 million Australian mangroves were wiped out. Video
The Taliban's broken promises
The tech aiming to prevent lost airline luggage
How repeating mantras 'repairs' your brain
The humiliating story that made me a break-up coach
Evacuated twice in a summer as France's fires burn
The best public pools around the world
Why open relationships are on the rise
The ejector seats that fire through the floor
© 2022 BBC. The BBC is not responsible for the content of external sites. Read about our approach to external linking.
By Vanessa Buschschlüter