West Brom's FA Cup fourth-round derby against Wolves was suspended in the second-half due to crowd trouble.
In the first match between the rivals in front of fans since 2012, players were taken off the pitch after Matheus Cunha doubled the lead for Wolves in the 78th minute at The Hawthorns.
Scuffles broke out in the stands following that goal and supporters entered the pitch, despite a large number of police attempting to calm the situation. Announcements urging fans to return to their seats had little impact, with riot police later entering the stadium.
West Brom defender Kyle Bartley was seen holding a child on the pitch, with players concerned for family members in the stands.
After a delay of almost half an hour, players returned to the pitch to warm-up, as the paramedics continued to deal with fans who had been injured. One man was seen with his head covered in blood as he was led away.
The match did eventually get back underway, 38 minutes after the referee had been forced to halt proceedings.
An FA statement read: "The disorder that occured at the Black Country derby between West Bromwich Albion and Wolverhampton Wanderers is completely unacceptable.
"Safety and security are of the upmost importance, and the behaviour of those involved was dangerous and inexcusable. We will be investigation these serious incidents alongside the clubs and the relevant authorities, and the appropriate action will be taken."
Tensions had run high throughout the match, which had been given the unusual kick-off time of 11:45am. Flares were thrown in the away end after Wolves opened the scoring, while Tommy Doyle had objects thrown at him by home fans as he prepared to take a corner.
A bottle was launched at Doyle in the closing moments of the match, as Wolves held on for a 2-0 win to book their place in the fifth round of the competition.
The delay to the match forced the fifth-round draw to be pushed back. Initially scheduled to take place ahead of Liverpool's match with Norwich, it is now set to be held at half-time of that match.
