ISTANBUL (AP) — Istanbul's governor says police have released 275 workers a day after hundreds were detained following a protest denouncing poor working conditions at the city's new airport.

State-run Anadolu agency quoted governor Vasip Sahin as saying Monday the construction company is trying to improve working conditions.

Arzu Cerkezoglu, head of the Confederation of Progressive Trade Unions of Turkey, told The Associated Press that over 500 workers were detained over the weekend, taken from their construction site sleeping quarters.

Local media said police used tear gas Friday to break up a protest by workers demanding better conditions, including improved safety. Another 20 were arrested Saturday as they demonstrated in support of the detained workers.

The new airport, one of President Recep Tayyip Erdogan's major constructions projects, is to open Oct. 29.