Updated

A former contractor for the U.S.-based coal company Drummond Co. has been convicted of murder and sentenced to nearly 38 years in prison as the mastermind of the 2001 killing of two union leaders.

The trial judge also ordered prosecutors to investigate Drummond's U.S.-based president and three current and former employees to determine whether they might also be responsible.

The killings are the subject of a U.S. lawsuit and have drawn considerable attention because several witnesses, including the convicted man, Jaime Blanco, allege senior managers of Alabama-based Drummond ordered them.

Drummond officials have denied any involvement in the killings. A company spokeswoman in Colombia had no immediate comment on the verdict, and a phone message seeking comment left at the company's headquarters in Birmingham, Alabama, was not returned.

Union leaders Valmore Locarno, 42, and Victor Hugo Orcasita, 36, were shot to death after being pulled from a workers bus by far-right militiamen, known as paramilitaries, after a shift at Drummond's La Loma mine in the northern state of Cesar.

Human rights and labor activists allege that Drummond colluded with paramilitary militias blamed for thousands of murders in Colombia, hiring them to silence opponents and suspected leftist rebels.

The company denies hiring militias and it is fighting a lawsuit filed by survivors of the slain men in an Alabama federal court that claims Drummond aided and abetted war crimes, including extra-judicial killings. Blanco is a key witness in that case.

The Associated Press learned Wednesday of the Jan. 25 verdict against Blanco, which is under appeal.

Judge William Andres Castiblanco sentenced Blanco, who ran a food services concession at the Drummond mine, to 37 years and 11 months in prison and fined him $369,000.

The judge said in an 81-page opinion that Blanco "took advantage of his closeness to commanders of the paramilitaries" to help him eliminate Locarno and Orcasita, who represented union members who had complained about his food service.

Blanco told the AP in an April 2011 jailhouse interview that Drummond's senior management ordered that the two union organizers be killed. He said his conviction would allow them to "wash their hands" and get the U.S. lawsuit dismissed. That case remains in pre-trial motions.

The attorney representing the plaintiffs, Terry Collingsworth, applauded Castelblanco's order that prosecutors investigate Drummond's president, Garry Drummond, as well as a former mine security chief and two Colombians to determine whether they share any responsibility for the killings.

But Collingsworth also said he was not hopeful that the order would lead to a Colombian criminal prosecution as a different trial judge made the same recommendation when he convicted Blanco's former assistant, Jairo Charris, in the same murders in 2009. Charris was sentenced to 30 years.

In an unrelated development earlier Wednesday, Colombia's Environment Ministry indefinitely suspended permission for Drummond to load coal onto ships at its port near the city of Santa Marta.

The order, which paralyzes the company's exports, comes after Drummond dumped at least 500 metric tons of coal into the Caribbean over two days last month. A company statement two weeks after the incident said one of its ships had to dump the coal because it was in danger of sinking in bad weather.

A ministry official, Luz Helena Sarmiento, said permission would not be restored until Drummond presented a new contingency plan for emergencies.

Drummond produces 24 million tons of coal annually in Colombia, the bulk of its production. It claims more than 2 billion tons in reserves.

A Drummond spokeswoman in Colombia, Wilma Calderon, said the company had no immediate comment on the government action or the verdict.