World snooker champion Mark Williams was forced to seek hospital treatment after suffering chest pains during the opening session of the second-round match against David Gilbert on Friday.

Williams experienced the pains as he lost the opening session against Gilbert 5-3 at the World Championship in Sheffield.

But the Welshman later revealed doctors are confident his health scare is not related to his heart.

World No. 3 Williams posted on Twitter that he was in the accident and emergency department of a local hospital, saying: "Couldn't stick the chest pains no more."

The 44-year-old informed tournament officials of the issue after the session and was advised by the on-call doctor to attend hospital.

Williams made his own way there and is understood to be with his wife Joanne and son Kian.

Williams posted an encouraging update during Friday evening.

"Doctors are confident it's not anything to do with my heart," he tweeted. "Awaiting more tests at 10 o clock."

The last-16 match is due to resume on Saturday at the Crucible and Williams hopes to be well enough to play.

Meanwhile, Australian Neil Robertson became the first player to reach the quarterfinals after beating Shaun Murphy 13-6 in the second round. Robertson will play either Stuart Bingham or John Higgins in the last eight.