The same day a militant group took hostage six foreign truck drivers, police discovered a decapitated body believed to be a Bulgarian trucker taken captive last month.

The body, found Wednesday night on the Tigris River in the town of Beiji, was in an orange prison-style jumpsuit that kidnappers have forced some captives to wear before beheading them, The Associated Press reported.

Bulgarian officials were attempting to verify if the remains found were those Ivaylo Kepov, one of two Bulgarians who were kidnapped June 29. Another beheaded body was found on the river July 14 and has been identified as the other Bulgarian hostage.

The AP reported that many of the nearly 70 people taken hostage in Iraq are truck drivers who haul cargo for private companies. The news organization also reported that truckers tend to be easier targets than other civilian employees for militant groups.

A militant group calling itself the “Black Flags” released a video Wednesday to a Dubai-based news channel showing six kidnapped foreign truckers – two Kenyans, three Indians and one Egyptian. However, the group listed an additional captive. Thursday the group released another video showing a third Kenyan, bumping the total number hostages thought to be held by the group to seven.

The group is demanding the withdrawal of civilian workers from Iraq. The group said in the video it would behead one hostage every three days until the conditions of release were met. Initially the home nations of the captives did not respond.

However, Indian, Kenyan and Egyptian officials are now working together to try to free the seven hostages, an Indian official in New Delhi told The AP. Kuwait and Gulf Link Transport Co., the company for which the captives worked, also issued a statement saying the company was working toward the release of the captives.

Kenya went on to respond to the militants’ demand Thursday by calling on its citizens to leave the country.

Moves such as those of Kenya and the Philippines, who withdrew workers from the country in exchange for the release of a Filipino hostage, have been met with criticism from the U.S. government as encouraging militant groups to strike out at civilian workers.