Missiles fired from a U.S. drone killed 13 civilians in Yemen on Thursday, according to Yemeni security officials. The people were traveling in multiple vehicles to a wedding party. 

Officials say the attack occurred in the city of Radda, the capital of Bayda province. According to The Washington Post, the blast left burned bodies and wrecked cars along the road. 

Radda, which is a stronghold for al-Qaeda, saw deadly clashes last year between armed tribesmen, who were backed by the military, and al-Qaeda gunman in an attempt to drive al-Qaeda out of the city. 

There were no immediate details about the strike. There are also conflicting reports as to whether or not militants were also traveling with the civilians, ABC News reports. 

A military official said that the drone thought the civilian wedding party was an al-Qaeda convoy. Tribesman were among those killed. However, one security official said al-Qaeda militants were believed to have been traveling with the civilians. 

If further investigations of the attack reveal that all of the victims were civilians, it could elicit anger from the government in Sanaa, and from the Yemeni public, who are already opposed to the U.S. drone program. Civilian deaths have infuriated local residents, and undermine U.S. efforts to get the public to turn against al-Qaeda. Yemen, like Pakistan, is beginning to call for a halt to U.S. drone strikes. 

The attacks in Yemen are part of a joint U.S.-Yemeni campaign against al-Qaeda on the Arabian Peninsula. Washington has deemed the militants in Yemen to be the most dangerous branch of the terrorist organization. 

The latest drone strike is the second since a car bombing and coordinated assault on Yemen's military headquarters, which killed 56 people, including foreigners. Al-Qaeda claimed responsibility for the attack, saying it was in retaliation for U.S. drone strikes. 

Yemen also beefed up its security forces in the region on Thursday in response to what the Interior Ministry called the threat of "terrorist plots" that targeted institutions and government buildings.