Fort Worth police said in a statement Saturday that officers were called to an apartment building around 2 a.m. about a possible assault. Police said Manziel was not arrested.
"The preliminary investigation determined that a possible assault had occurred in that jurisdiction or multiple jurisdictions," the police statement said. "The complainant was uncooperative with officers on scene, and they were unable to locate a crime scene within the Fort Worth jurisdiction, however, our officers prepared a report nonetheless, and that information was forwarded to detectives for further investigation."
The police report stated that the woman was concerned about the well-being of Manziel, which launched an effort to locate him that involved the police's helicopter unit. Police later determined that Manziel was safe and not in danger.
Fort Worth police said they are working with Dallas police to determine if any criminal offenses occurred.
The Browns said they would have no comment at this time. NFL spokesman Greg Aiello told ESPN the league was aware of the incident and "looking into it.''
In October, Manziel and his then-girlfriend were questioned by police in Northeast Ohio following an argument that started on the highway and extended near Manziel's suburban home. Several witnesses called police after seeing Manziel and a woman arguing in a vehicle. The argument escalated to the point that she tried to leave the car as it exited a highway.
Avon, Ohio, police questioned Manziel and the woman but made no arrests. Both Manziel and the woman admitted to arguing, and Manziel told police they had been drinking earlier in the day. The officer made the determination that Manziel was not intoxicated. The NFL investigated the incident and announced in November that Manziel would not be disciplined.
The Browns expressed concern earlier this week over reports that Manziel was spotted in a Dallas bar, at a Fort Worth Liquor store and a concert at a Dallas nightclub, the Fort Worth Star-Telegram reported. Video of Manziel made the social media rounds.
"I haven't seen them, but I would care about it just because I want all of our guys to represent themselves well and be responsible in terms of their behavior off the field,'' Sashi Brown, the Browns' executive vice president of football operations told Cleveland.com's Mary Kay Cabot at the Senior Bowl this week.
"We want all of our guys to go out and come back in shape and be ready to go. The thing for him obviously is to demonstrate to teammates, to our fans, and to folks in the building that this is going to be the most important thing in his life.''
A source told ESPN that new head coach Hue Jackson made it clear when he interviewed for the job that he wanted the Browns to move on from Manziel.
But on Thursday, Browns owner Jimmy Haslam said he was hopeful the team's relationship with Manziel could be mended but only if the 2014 first-round pick lived up to expectations.
"Oh, yeah, I don't think there's any question about that," Haslam said Thursday night at the Greater Cleveland Sports Awards. "We talked to Johnny before he left. I know a big deal was made that Hue hasn't called Johnny yet. Well, we've got 53 players on the active and 10 more and there were a couple of other real prominent players that he just talked to in the last day or two, so I'm sure he'll get around to talking to him. I think we made clear, I don't have any different feelings than we had on Sunday, Jan. 3. I think Johnny made progress on the field last year. I think that's undeniable. We have a certain expectation for our players and that includes Johnny and he's got to live up to those expectations."
Jackson told Cleveland.com this week that he has reached out to a number of players, but that Manziel wasn't "in the first batch.''
The Browns selected Manziel with the No. 22 pick in the 2014 draft. Cleveland has the No. 2 overall pick in the upcoming NFL Draft.
Manziel reportedly was in Las Vegas on the Saturday night before the Browns' final regular-season game despite being in the NFL's concussion protocol that sidelined him for the game against the Pittsburgh Steelers. He missed his mandatory concussion treatment on gameday at the team's facility and was fined.
Manziel was videotaped drinking, including on Christmas Eve, during the season. He spent 73 days in inpatient addiction-rehab center in the offseason.
Less than a week after being named the Browns' starter in mid-November, another video surfaced online of Manziel holding a bottle at an Austin, Texas, club during the team's bye week. Manziel was demoted to the third string for the next game.
Manziel, 23, finished his second season with 1,500 passing yards, seven touchdowns and five interceptions in nine appearances (six starts) and a passer rating of 79.4. He rushed for 230 yards.