An anti-doping investigation has rocked the AFL, with Essendon facing scrutiny over supplements supplied to their players last year.

While the Bombers are confident performance-enhancing drugs (PEDs) are not involved, the Australian Sports Anti-Doping Authority will lead the joint investigation with the AFL.

After two months of rumours, Essendon announced on Tuesday they had gone to the league because of concerns the club had about supplements.

The Bombers will give no details about the investigation – who is involved, which substances were allegedly taken or the circumstances.

“Over the last 48 hours, Essendon have received information about supplements that have been given to our players as part of the fitness program in 2012,” club chairman David Evans said.

Asked directly if he feared players might have taken PEDs, Evans said “no”.

“The information we’ve gathered over the course of the last 24-48 hours is slightly concerning and we want to dig a bit deeper,” he added.

“But we want some experts to help us do that.”

Evans, coach James Hird and club chief executive Ian Robson were grim-faced as they fronted a media conference on Tuesday afternoon to announce the investigation.

They had met with senior AFL officials earlier in the day.

Essendon and the AFL said in separate statements that the club approached the league about the potential scandal.

It is unclear how long the investigation will take.

“We certainly don’t want to be sitting here, talking about this,” Hird said.

“We want to get this investigation started. We want to get it done. We want to come out with a clean bill of health.

“We want to move on with the footy season.”

Hird was also confident the players had not taken banned substances.

“The supplements our players were given, in my opinion and my knowledge, were all approved and within the regulations we all play the game by,” he said.

“I’m very disappointed – shocked is probably the best word.

“I believe we followed processes, we put in place the right sort of processes.

“My understanding is we worked within the framework given to us by the AFL and WADA.

“I’m shocked to be sitting here.”

Evans and Hird said the club wanted a clean bill of health about the supplements that players had taken.

“The investigation takes its course from here and we’ll learn more,” Evans said.

“I don’t have all the answers, but as you would agree, this is a minefield.

“It takes experts … we’ll use them to help us with our findings.”

Essendon’s fitness program came under intense scrutiny last season when they suffered a shocking run of soft-tissue injuries and plummeted out of the top eight.

Sports scientist Stephen Dank has since left the club.