DALLAS (REUTERS) - A paramedic in West, Texas, has been arrested for possession of an explosive device, a federal official said on Friday, but it was not clear whether there was a connection to a deadly explosion last month at a fertiliser plant in the town.

Texas officials also announced on Friday that they had opened a criminal investigation into the April 17 explosion that killed 14 people and injured about 200 others. They made no mention of an arrest.

United States (US) Bureau of Alcohol, Tobacco, Firearms and Explosives spokesman Franceska Perot identified the man arrested as Bryce Reed.

A source familiar with the matter said it was not clear that Reed's arrest was linked to the blast at West Fertiliser Co.

"I don't know that they're making that connection," said the source, who asked not to be identified because she was not authorised to speak to the news media.

An employee at McLennan County Jail, who also asked not to be identified, said Reed, 31, was brought to the jail at 2am and handed over to federal agents at 8am.

A call to Reed's cell phone went unanswered on Friday and Reed's wife, Brittany, said in a text message that she could not comment.

The state fire marshal's office has said that ammonium nitrate stored at the plant detonated in the explosion but that the cause of the fire and blast were still being investigated.

"This disaster has severely impacted the community of West, and we want to ensure that no stone goes unturned and that all the facts related to this incident are uncovered," Mr Steven McCraw, director of the Texas Department of Public Safety, said in a statement announcing that the Texas Rangers and McLennan County Sheriff's office would join in a criminal investigation.

SURVIVOR OF BLAST

Bryce Reed told Reuters last month that he had been a paramedic for 13 years and that he had worked in combat zones overseas as a contract paramedic.

Bryce and Brittany Reed said that they were listening to music at their home when they heard the town's siren and jumped into their truck to warn people nearby.

"Get your kids and go!" the couple said they yelled at residents of an apartment complex near the plant. They said they were about 50 to 75 yards from the plant when the blast rocked their vehicle.

The force of the blast also destroyed their home, blowing the doors off and filling their two-year-old daughter's bedroom with shards of glass, Bryce Reed said.

"Had she been in there, she'd be dead," he said. "We've lost everything. But my family is alive and that's enough for me."

He also said that he lost his best friend, volunteer firefighter Cyrus Reed, in the blast.

The two were not related, but were so close they considered each other brothers, Bryce Reed said at the time.

"There's no words to convey the magnitude of this incident," Reed said last month.

Earlier this week, Bryce Reed wrote on his Facebook page that he was "incredibly emotional" and felt he was being attacked by people who had suggested he was profiting from his efforts to honour the fallen firefighters and emergency medical service workers through a number of media interviews he had given since the blast.

"Integrity is so hard, especially when it is attacked. I am so sick of being strong. I am so sick of crying. You try to do the right thing, and get kicked for it," he wrote in a post on Monday. "I am not crazy, I'm lost."