UK Labour leader Jeremy Corbyn is unharmed after he was pelted with an egg during a visit to a North London mosque Sunday, a Labour Party source confirmed to CNN.

A 41-year-old man was swiftly detained following the incident and arrested on suspicion of assault, the Metropolitan Police said in a statement. He remains in custody at a police station in North London.

The attack happened as Corbyn was visiting Finsbury Park Mosque and Muslim Welfare House for Visit My Mosque Day. Over 250 Mosques across the UK held welcome days on Sunday “to welcome in their neighbours from all faiths and none and (build) bridges across communities,” according to their website.

The motive behind the egging is as yet unknown, but it comes at a fraught time politically for the Labour leader, who recently announced his support for a second Brexit referendum and faces continued criticism over his handling of anti-Semitism within his party.