CALCUTTA, India?Police arrested three Bangladeshis and three Indian teachers at an Islamic school and charged them in an attack on a U.S. cultural center that left four policemen dead, officials said Wednesday.

The Indian government appeared to back down from its earlier assertion that the shooting in Calcutta was a terrorist attack, saying it was too early to tell the motive, after the United States said it was not certain the attack was political.

India initially accused Islamic militants and Pakistan’s spy agency after gunmen on motorcycles sprayed the American Center in Calcutta with gunfire on Tuesday, killing four policemen and wounding 20 people. Pakistan denied any role.

Bangladesh also denied any involvement, saying it would not allow its territory to be used for terrorism against other nations.

U.S. officials said Tuesday the attack may have been criminal, targeting the policemen.