At least 16 miners have been killed and nine others are missing after an explosion at a mine in eastern Ukraine, the country's emergencies ministry said.
Two more mine workers received burn injuries and were admitted to hospital after Friday's blast in the Lugansk region, the ministry said in a statement.
Investigators are working to establish the cause of the explosion, which occurred at 1:57am local time [22:57GMT].
Interfax news agency quoted a regional mining official as saying the explosion was caused by a concentration of methane gas inside the mine, where 252 people were working at the time.
The explosion is the deadliest since 2007, when a methane blast at a nearby mine killed more than 100 people.
In 1992, 58 people were killed in a methane explosion at the same mine. Last month, a fire occurred at the mine but no one was hurt.
Yury Boiko, the country's energy minister, went to the scene of the accident to personally take charge of the rescue operation.
The mine is owned by Krasnodon Coal, Ukraine's second largest mining company and has been in operation since 1980.
Ukraine produced more than 75 million tonnes of energy and coking coal last year, but has been plagued by accidents caused by poor infrastructure and lax safety regulations.