England forward Dylan Hartley has been cited for alleged foul play during Northampton's European Cup defeat against Ulster.
European Rugby Cup (ERC) announced on Monday that Northampton captain Hartley has been reported by match commissioner Jean-Claude Legendre for striking opposite number and Ulster hooker Rory Best with his arm in last Friday's clash.
Hartley will face a disciplinary hearing on a date to be confirmed.
Recommended International Rugby Board sanctions for striking with the fist or arm range from a two-week ban at the low end to a maximum 52 weeks.
"Hartley is alleged to have struck Ulster Rugby forward Rory Best with his arm during the second half of the match at Franklin's Gardens," ERC said in a statement.
"Details of the hearing date and the appointed independent judicial officer will be announced shortly."
Hartley's citing will add an extra edge to next weekend's return fixture between Northampton and Ulster, which is a must-win match for Saints, who are eight points behind their Pool 4 rivals.
The 26-year-old had only just returned to action after suffering an injury that sidelined him from England's recent international campaign, but he has a chequered past in disciplinary terms.
He was banned for 26 weeks in April 2007 after being found guilty of eye-gouging Wasps' players James Haskell and Jonny O'Connor.
It was a punishment that dashed his hopes of being part of England's World Cup campaign in France later that year.
Earlier this year, Hartley was banned for eight weeks after being cited for biting Ireland flanker Stephen Ferris during a Six Nations clash at Twickenham.