A Casper man pleaded not guilty Tuesday to providing two underage girls with marijuana while carrying on sexual relationships with them.

Manuel Nikolas Sambrano, 24, appeared in Natrona County District Court to answer to eight charges ranging from second-degree sexual abuse to delivery of marijuana. His charges carry a maximum combined sentence of 150 years behind bars.

Shackled and dressed in an orange jail uniform, Sambrano spoke only to answer procedural questions and enter his pleas. He addressed Judge Thomas Sullins in a soft voice that was barely audible to spectators in the back of the courtroom.

Investigators suspect Sambrano had sex with the girls, ages 13 and 16, on multiple occasions earlier this year. Both girls told detectives he gave them marijuana and one accused him of also giving her cigarettes and alcohol.

In an interview with detectives, he initially denied having sex with the girls, but later admitted to the allegations, police say. Sambrano also reportedly told them he provided the 16-year-old girl with marijuana 10 different times and gave the younger girl the drug on two occasions.

Detectives arrested Sambrano after driving by the 13-year-old girl's home in August and seeing him sitting on the doorstep with her, police say. Since that time, he has remained jailed in lieu of $50,000 bond.

Authorities began investigating Sambrano in July after the Wyoming Department of Family Services received a report that he had brought obviously underage girls to his work.

In early August, the 16-year-old girl told investigators she "basically traded sex" with Sambrano for drugs, cigarettes and alcohol, according to a police affidavit. The girl said she had met him through his work.

The 13-year-old girl also spoke with authorities and accused Sambrano of having sex with her, the affidavit states. She said the two had talked about her age before having sex for the first time.

A trial date for Sambrano has not been set.

Reach crime reporter Joshua Wolfson at (307) 266-0582 or at josh.wolfson@trib.com. Visit tribtown.trib.com/JoshuaWolfson/blog to read his blog.