Police said they received a report of a fan making alleged racist gestures in the game against Manchester City.

City said they were working with police "regarding an instance of objects being thrown on to the field of play".

A 41-year-old man has been held on suspicion of a racially aggravated public order and remains in custody.

On Saturday, a man was filmed apparently making monkey gestures and sounds towards Manchester United players during the derby at City's Etihad Stadium.

It happened as United midfielder Fred went to take a corner in the second half and appeared to be hit by an object hurled from the crowd.

After the match, the 26-year-old Brazilian said: "On the field, I didn't see anything. I saw it only in the locker room afterwards. The guys showed me. [A man] even threw a lighter and it hit me."

United boss Ole Gunnar Solskjaer said: "Fred and Jesse [Lingard] were in the corner, taking a corner, and I've seen the video, heard from the boys."

He said the apparent behaviour of the supporter caught on camera was "unacceptable".

In a statement, Manchester City said they were working with police to identify offenders, adding: "The club are also working with GMP regarding an instance of objects being thrown on to the field of play.

"The club operates a zero-tolerance policy regarding discrimination of any kind, and anyone found guilty of racial abuse will be banned from the club for life."

After social media speculation that the person allegedly making the monkey gestures worked for the infrastructure firm Kier Group, the company tweeted an employee had been suspended "pending an investigation".

The company added: "We're aware of a video circulating on social media. We take allegations and instances of racism very seriously and are currently investigating potential links between the individual involved and Kier.

The FA said it would investigate the incident, while the Premier League said it "will not tolerate discrimination in any form".

"If people are found to have racially abused Premier League players they deserve to be punished and we will support any action taken by the authorities and the clubs," a Premier League spokesperson said.

The incident comes a year after racism in football hit the headlines after City striker Raheem Sterling was subjected to racist abuse at Stamford Bridge, which led to a permanent ban for a Chelsea supporter.

Sterling was also one of a number of England players who faced monkey chants and Nazi salutes in Euro 2020 qualifiers this year.

Fred said the alleged incidents on Saturday showed "we are still in a backward society".

United won the match 2-1 after goals from Marcus Rashford and Anthony Martial.