Twickenham and Newcastle yesterday opened inquiries into allegations that the Newcastle prop Paul Van Zandvliet bit the England flanker Neil Back.

Back's own club, Leicester, initially said they too would look into the matter but later added that they would not be lodging a complaint.

Yesterday's flurry of activity came after newspaper pictures showed Van Zandvliet apparently pressing his teeth into the left side of the England forward's head during Monday's ill-tempered match at the Gateshead Stadium. Back said he had been bitten on the thumb but knew nothing about being bitten on the head.

Predictably, Van Zandvliet, whose home was door-stepped by journalists yesterday, decided to say nothing about the incident in a match which overflowed with violent illegality.

At one stage Back picked up Rob Andrew, Newcastle's out-half and director of rugby, and threw him over his shoulder. Later Leicester's Will Greenwood was sent off by the referee Ed Morrison for butting Andrew, an offence likely to attract a 60-day ban and rule the centre out of England's summer tour.

The Van Zandvliet incident came to light only when a blow-up of a still photograph showed the prop's open mouth in contact with Back's head.

Back said: "I can't remember being bitten in the head at any stage. I was bitten on the thumb at some stage in the match but I have no complaint because, in the act of pushing a player away, my thumb could have been accidentally bitten."

These comments seemed to exonerate Van Zandvliet from any wrong-doing, and are bound to weigh heavily with the RFU's inquiry tribunal. However, Twickenham is still concerned about rugby's image so soon after the Bath prop Kevin Yates was banned for six months for biting off part of Simon Fenn's ear.

Serious questions have been raised by the calculated mayhem that players inflicted on one another throughout the match, which Newcastle won 27-10. Who bit Back's thumb, if indeed it was a bite? How did the Leicester open-side's ear come to be bleeding so profusely? Indeed was Back, who has a reputation for fair play among his peers, the unlucky victim of retaliation by other Newcastle players for acts of violence inflicted on them?

Last month Van Zandvliet did himself no favours when he was seen kicking away the legs of Gloucester's Mark Mapletoft in a live televised match at Kingsholm, an offence the referee said he did not see but which warranted a red card.

Monday's referee Morrison said yesterday that the Back incident would not figure in his report. Morrison, who issued yellow cards to three players in addition to dismissing Greenwood, said he did not see any biting.

"I cannot comment on something I didn't see and I won't be sending in a report on it to the RFU," said Morrison, who refereed the 1995 World Cup final. "The first I heard about it was when I saw it in the papers."

Andrew maintained a low profile yesterday, saying only that the club would be carrying out an internal investigation, and Leicester's chief executive Peter Wheeler suggested that the seriousness of the incident might have been exaggerated.

Wheeler, a former England hooker, said: "In these rucks and mauls you do get players pressed very tightly together and, if somebody gets pressed and somebody has their mouth open, it can be misconstrued in some circumstances."

Leicester team manager Dean Richards said he had spoken to Andrew about the incident but that was as far as the club would take the issue.

"I have spoken to Rob Andrew and he understands our feelings in the matter," he said, "From our point of view, on the evidence we have, the episode is now closed."

He said Leicester will, however, be looking into the Greenwood sending-off.

Van Zandvliet was yesterday remanded to appear at Gateshead Magistrates Court charged with selling false clothing including brand names such as Adidas, Nike and Calvin Klein at Blaydon rugby club last July. Van Zandvliet, of North Shields, pleaded not guilty.