Ronnie O'Sullivan could be set for a fine after playing with no shoes on for some of his 2015 World Snooker Championship opener against qualifier Craig Steadman on Tuesday.

In terms of the scoreline, five-time champion O'Sullivan enjoyed a relatively comfortable time of it, emerging from the first session of the encounter - that had begun with him making a century break - with a 7-2 lead over Crucible debutant Steadman.

But the world number two, who suffered a broken ankle towards the end of last year, appeared in discomfort due to his footwear at one point and opted to remove his shoes, briefly playing on in his socks.

He subsequently borrowed a pair of shoes from tournament director Mike Ganley and put them on, but Press Association Sport understands the World Professional Billiards and Snooker Association will look into the matter to consider whether it constitutes a breach of its rules about members' dress code, which could see O'Sullivan handed a fine.

Meanwhile, two-time finalist Ali Carter, given the all-clear from lung cancer in December, made a winning start to his campaign as he completed a 10-5 win over veteran Scot Alan McManus.

Carter finished the job from a 6-3 overnight lead to set up a last-16 meeting with Australia's 2010 champion Neil Robertson, the world number four.

"I didn't feel as if I played great, but I competed in all departments and won quite convincingly in the end," Carter told a press conference.

"I have some good memories here - the only thing I have left to do is win it, and that's what I'm here to do."

Earlier, world number three Ding Junhui overcame the embarrassment of missing out on a maximum break after forgetting he was on track for a 147 to book his place in the second round.

China's Ding was trailing opponent Mark Davis 5-3 and was at the table on a break of 96 when he inexplicably screwed back for the blue ball instead of playing for the black.

The apparent lapse in concentration left the audience stunned, while Ding covered his head in his hands then proceeded to smile after realising his error.

Following his mistake, Ding regained his composure and went on to claim a 10-7 win over Davis.

Ding admitted he did not realise he had been on course for a maximum break until the crowd gasped after the shot which put him on the blue.

"I didn't even know about the 147," Ding said.

"I potted the red and heard the noises from the crowd and I realised what I had done. The blue was on its spot and I was just trying to make a century, I wasn't even thinking about making the 147. ''

Ding will play John Higgins in the next round, and added: ''I've played him many, many times. I've learned a lot from him. I've got more confidence to play him now.''

The evening session saw Northern Ireland's Mark Allen secure his second-round place by wrapping up a 10-3 win over Wales' Ryan Day.

Allen had built up a 6-3 lead from the first session earlier in the day and swiftly finished the job later on to progress to an encounter with world number five and 2013 finalist Barry Hawkins.

Allen, who won nine frames in a row having been 3-1 down to Day at one point, said: "That was only my C game there today.

"I'm nowhere near my best yet and, if I bring my best in this two weeks, then I expect to be here at the end of the two weeks."

On the other table, two of Day's compatriots got their first-round match under way, with two-time runner-up Matthew Stevens establishing a 7-2 lead over Mark Williams, the 2000 and 2003 champion.

The winner of that contest will face the victor from O'Sullivan-Steadman in round two.