SAO PAULO, Brazil, Oct 19, 2007 (AFP) - World championship leader Lewis Hamilton faces a possible penalty after his McLaren team flouted the tyre regulations in opening practice ahead of the decisive Braziliaan Grand Prix here Friday.

Hamilton topped the times ahead of his McLaren team-mate defending title-holder Fernando Alonso after Friday´s opening practice sessions at Interlagos.

But the British rookie then went off to be interviewed by the the sport´s governig body the FIA after using two sets of wet tyres in the morning session.

Although breaking the rules it is not expected any punishment possibly in the way of a fine would impinge on his title bid in the closing race of the season.

Hamilton leads Alonso by four points going into Sunday´s showdown in which Finn Kimi Raikkonen can also clinch the title for Ferrari if he wins the race and the two McLaren men fail to score sufficient points to take the title.

Hamilton shrugged off the tyre controversy to clock a fastest time of one minute and 12.767 seconds on his first day appearance at the famous old Interlagos circuit to finish 0.122 seconds ahead of Spaniard Alonso, 26.

Raikkonen was fourth in practice, one place behind his Ferrari team-mate local hero Felipe Massa of Brazil who won last year´s race.

Hamilton, looking supremely cool and confident, drove with care and caution on drying circuit after a day of steady rain, learning his way round the demanding and undulating curves of the track.

"It was pretty evil out there in the wet this morning," he said before second practice began in the afternoon.

Raikkonen topped the earlier session, but Hamilton, showing great composure and judgement, worked his way to the top of the time-sheets.

Italian Giancarlo Fisichella was fifth for Renault ahead of Poland´s Robert Kubica in a BMW Sauber.

Hamilton was one of three drivers declared to be under investigation by the race stewards over the tyre rules.

Hamilton, Briton Jenson Button of Honda and Japanese Takuma Sato of Super Aguri were all deemed to have used two sets of wet weather tyres during the first free practice session.

This, a statement said, was in breach of the Sporting Regulations.

It is unlikely to be treated too seriously, as no direct performance advantage was gained, but seasoned observers suggested that each of the drivers could be fined or face further sanctions.

Article 25.3 of the F1 Sporting Regulations states: "No driver may use more than one set of wet and one set of extreme weather tyres during P1 and P2."

The issue was brought to the race stewards´ attention by FIA technical delegate Jo Bauer.

All three drivers have been summoned to see the stewards individually following the end of the second practice session later this afternoon.