Robin Thicke and Paula Patton's custody battle over six-year-old son Julian continues to heat up after cops were called on Thurs. afternoon.

According to TMZ, the incident took place at the same Malibu, California park the estranged exes meet every week to exchange custody of Julian. However according to sources, Patton showed up an hour late and refused to hand Julian over to the court appointed monitor.

The monitor is being utilized due to the restraining order in place against Thicke. Some sources at the scene claim that Thicke was in violation of the restraining order, standing only feet away from Patton. However, other sources say that Thicke remained in his car the entire time. Patton's people called the police and Julian eventually left the scene with his mom.

Patton and Thicke are in the middle of a custody battle that resumes in court on Feb. 24. Patton was granted full custody of Julian until that time, with Thicke given visitation rights three days a week at a neutral location.