Ray J and Princess Love got into a heated fight … and we’re told things were so bad, police got involved and detained Ray in the back of a squad car.

Law enforcement sources tell TMZ … Ray J came home from a tour Thursday afternoon and he and Princess Love started fighting about their pending divorce.

We’re told Princess called LAPD, claiming Ray J was being aggressive, yelling, and possibly under the influence.

Our sources say when cops arrived at the house, they detained Ray and slapped on a pair of handcuffs … keeping him in the back of a black-and-white to de-escalate and figure out what the heck happened between them.

After speaking to both parties, we’re told police determined no crime had been committed. Ray J was taken out of cuffs, released, and went on his way.

Some of Ray’s interaction with police was recorded on video and posted online … and you can hear him thank the officers for the way they handled the situation.

Ultimately, we’re told police took a domestic-violence incident report … but again, cops determined there was no crime here, and Ray J was never placed under arrest.

We reached out to reps for Ray and Princess … so far no word back.