Pittsburgh, PA (AP Newswire) – Artwork valued in the thousands of dollars was stolen from several artists at Pittsburgh’s Three Rivers Arts Festival.

The thefts occurred between Saturday night and Sunday morning.

The artists arrived to find their works gone.

The festival has 24-hour security and it’s not clear how some of the larger pieces were stolen without anyone noticing.

In a statement, the Pittsburgh Cultural Trust called the thefts “an unfortunate occurrence.” It has increased security in the market area.