(CNN) -- Ukrainian President Victor Yanukovych declared Sunday a national day of mourning after 37 people died Friday in incidents at two mines.
An explosion at the Sukhodolskaya-Vostochnaya mine in eastern Ukraine killed 26 people and injured two, according to the Ukrainian Emergencies Ministry. The cause of the blast, which occurred 915 meters (3,000 feet) underground, was under investigation, the agency said.
In addition, 11 others were killed Friday in the Bazhanov mine in southeastern Ukraine when a 65-meter (213-foot) building collapsed, the ministry said. More than 500 miners were able to escape. Three miners sustained "moderately severe" injuries, and one was in "very serious condition," officials said. The reason for the collapse was under investigation.