BAGHDAD, Iraq (CNN) -- A U.S. Apache helicopter went down in Iraq on Friday, Pentagon officials said, the fourth helicopter to crash in two weeks.

The U.S. officials could not say whether the AH-64 crashed or was brought down by insurgent fire or whether there were casualties.

An official with Iraq's Interior Ministry, however, said earlier Friday that Iraqi soldiers in Taji, about 12 miles north of Baghdad, reported a U.S. helicopter was seen going down after coming under insurgent fire.

Witnesses later told The Associated Press that the wreckage was spotted near a fuel storage complex in Mashhada, near Taji, and that U.S. troops had sealed off the area.

Nineteen Americans were killed in the three previous incidents.

Of those, two U.S. troops were killed when another Apache was lost during fighting with insurgents last weekend in Najaf.

Last week, a U.S. helicopter providing air security for two U.S. Embassy officials came under heavy fire and crashed in eastern Baghdad, killing five employees for the Blackwater private security company. Three Iraqi insurgent groups claimed responsibility for the attack.

On January 20, a U.S. military Black Hawk helicopter -- believed to have been downed by a shoulder-fired missile -- crashed in Iraq's Diyala province, killing 12 U.S. soldiers on board.