The Independent Office for Police Conduct announced Wednesday an investigation into West Midlands Chief Constable Craig Guildford, who resigned in January over the decision to ban Israeli Maccabi Tel Aviv fans from a match between Maccabi Tel Aviv and Aston Villa in Birmingham, England.

“Former West Midlands Police Chief Constable Craig Guildford, plus three officers and a staff member, have been advised their conduct is being investigated by the Independent Office for Police Conduct relating to the Maccabi Tel Aviv supporter ban in Birmingham,” the IOPC wrote in a statement.

“Having examined all evidence currently available to us, we have assessed that there is an indication Mr. Guildford, a senior officer, and a staff member may have committed gross misconduct. They have been served notice that we are investigating their conduct,” the statement added.

The IOPC said that it believes that Guildford did not perform due diligence in overseeing intelligence that turned out to be faulty and that presented the police with an imbalanced view of the Israeli fans.

At the time, the ban elicited strong condemnations from both the Israeli and British governments, as well as local groups who accused West Midlands Police of failing to coordinate with the local Jewish community, of using an artificial intelligence chatbot to search for a basis on which to justify the ban, and of citing a nonexistent match between Maccabi and West Ham. An investigation found that the police first implemented the ban and then retroactively tried to justify it, using false intelligence and making false statements about it.

The police had claimed that intelligence from the Dutch police showed that the Maccabi fans presented a high risk to pro-Palestinian supporters because of their alleged violent confrontations at a match in the Netherlands. The police alleged that Dutch intelligence informed them that it had dispatched 5,000 police officers to quell the violence and that an Israeli fan threw a Muslim fan into a canal.

The Dutch denied those intelligence reports and said they were false. They had, in fact, dispatched 1,200 officers, and it was a Muslim fan who threw an Israeli fan into the canal.

At the time, Home Secretary Shabana Mahmood said she lost confidence in Guildford’s ability to lead the West Midlands Police force.

“The findings of the Chief Inspector were damning,” she said. “They set out a catalogue of failings that have harmed trust in West Midlands Police.”