what bipolar meds can cause a positive drug test?

My son was arrested and taken to a hospital last month after exhibiting behavior that was dangerous to himself.  He was blood tested and kept in the ER for hours and when he found out he was going to stay at hospital that night tried to leave and was arrested for disorderly conduct and taken to the county jail instead that night.  He was given a urine test there that was negative for drugs and transferred to a psychiactric hospital two days later. He stayed a week at hospital and was discharged with medication (I don't know the name) and a diagnosis of bipolar, manic phase, exacerbated.  Today he went to court for the disorderly conduct charge, was again drug tested, this time test was positive.  He does have a drug hx of meth use but denies usage at this time knowing he would be in court today.  Thus my wondering if his bipolar med could have caused a false positive drug test.  He was again taken to jail where he's to stay until a bed becomes available at a rehab facility.  None of this was ever about drugs but seems to have taken a path in that direction.