By LIBARDO CARDONABOGOTA, Colombia (AP) â¿¿ 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 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.