LONDON British police said on Tuesday their investigation into the death at the weekend of Nottingham Panthers ice hockey player Adam Johnson would take some time, saying they were seeking the advice of experts about the incident.

Johnson, 29, received emergency treatment following what his club called a "freak incident" during a match against Sheffield Steelers in Sheffield, northern England, on Saturday.

British media reports said his neck had been cut by a skate blade, and the Panthers announced on Sunday that Johnson, an American who joined the club in August having previously played in Germany and Sweden as well as in the United States' National Hockey League (NHL), had died.

"Since Saturday, detectives have been carrying out a range of enquiries including reviewing footage, talking to witnesses and seeking the advice and support of highly specialised experts to seek to understand the circumstances surrounding what happened," South Yorkshire Police said in a statement.

Police said it was standard practice to examine all sudden and unexpected deaths to provide findings for a coroner, and they were also working closely with the local council's health and safety department.

"Our officers have now left the scene, however due to the complex nature of this tragic and unprecedented incident, it is likely the wider investigation will take some time," the statement said.

"We continue to encourage the public to avoid speculation, including on social media, while we continue our enquiries and will provide updates when appropriate."

The English Ice Hockey Association (EIHA), which is the sport's governing body in England and Wales, said on Monday the safety of players must take precedence above all else and made neck guards mandatory from Jan. 1 for all on-ice activities.

The EIHA did not make the neck guards mandatory with immediate effect due to anticipated supply issues but made a "strong recommendation" that players at all levels across English Ice Hockey start using a neck guard.

(Reporting by Michael Holden; Editing by Christian Radnedge)