Three of Maria Sharapova’s major sponsors are cutting ties with the Russian tennis star after she acknowledged failing a doping test at the Australian Open.

Sportswear giant Nike, Swiss watch brand Tag Heuer and German luxury car company Porsche moved quickly to distance themselves from the five-time grand slam winner after she announced the positive test at a news conference in Los Angeles on Monday.

“We are saddened and surprised by the news about Maria Sharapova,” Nike said in a statement.

“We have decided to suspend our relationship with Maria while the investigation continues. We will continue to monitor the situation.”

TAG Heuer said its deal with Sharapova will not be renewed. The sponsorship expired at the end of 2015 and discussions had been taking place on how to extend it.

“In view of the current situation, the Swiss watch brand has suspended negotiations, and has decided not to renew the contract with Ms Sharapova,” TAG Heuer said in a statement.

Porsche said in a statement Tuesday that it has “chosen to postpone planned activities” with Sharapova “until further details are released and we can analyse the situation.”

Sharapova said she failed a doping test at the Australian Open in January for the little-known drug meldonium, which became a banned substance under the World Anti-Doping Agency code this year.

The former world No.1 took full responsibility for her mistake and could face a lengthy ban from the International Tennis Federation, possibly ending her season and preventing her from competing for Russia at the Olympics in Rio de Janeiro.

The 28-year-old Sharapova said she has been taking meldonium, a blood flow-promoting drug, for 10 years for numerous health issues.

Meldonium was banned because it aids oxygen uptake and endurance, and several athletes across international sports have already been caught using it.