At least 17 people were killed and 16 injured in an explosion at a bank in Karachi, Pakistan's largest city, on Saturday.
Police spokesman Sohail Jokhio said the blast was apparently caused by something igniting gas that had accumulated in a sewer beneath a local bank in the Shershah industrial area.
“Sixteen were brought injured to hospital,” Karachi's administrator Murtaza Wahab said in a tweet.
The powerful blast destroyed the HBL bank building, footage broadcast by local television stations showed.
The floor was blown out and furniture was covered in sewage from below. The impact of the blast damaged several cars parked nearby and threw debris on to a petrol station on the other side of the building.
Mr Jokhio said it was not yet clear what ignited the gas but a team of explosives experts would investigate.
In statement on Twitter, HBL, Pakistan's largest lender, said an explosion had damaged its Shershah branch and caused casualties and injuries.
“Our sympathies are with the bereaved families,” it said.
Senior police officer Sarafar Nawaz Shaikh said investigators were not ruling out the possibility that the explosion was the work of extremists.
“We will come up with a clear version once the explosives experts complete their job,” he said.
Witness Mohammad Sameer said he had been in the crowded bank branch but left moments before the explosion. He said he rushed back to help rescue people.
“Thank God I left the venue, otherwise I would also been among the affected ones,” Mr Sameer said.
Many sewer channels in the city have been covered, mostly illegally, by concrete structures built over them.
Mukhtar Abro, a local administrator, said illegal construction had taken place over the channel where the explosion took place.
Residents had been under notice to vacate, and the structures were due to be demolished, said the official.