Stewart, 52, injured himself at the studio where the long-running police drama is filmed, the Times of London said Wednesday.
"We can confirm an incident occurred yesterday following a meeting with Jeff Stewart, when it was discussed that Jeff's contract would not be renewed," a representative for the ITV1 show told the newspaper. "Our primary concern is for Jeff Stewart's welfare. We are doing everything we can to ensure Jeff is getting the help he needs, and would ask that his privacy is respected at this difficult time. All our best wishes are with Jeff."
Stewart has worked on the show since it first aired in 1984, appearing in more than 300 episodes.
The actor, who has admitted he suffers from depression, was suspended from his job for a week last month after reportedly losing his temper on set, the Times said.