The suspect arrested in connection with the Borussia Dortmund bomb attack had no Islamic extremist motive and instead hoped to profit from the blasts, German prosecutors say.

Investigators found notes at the scene claiming responsibility in the name of Islamic extremists, but quickly doubted their authenticity - as ITV News Security Editor Rohit Kachroo noted.

The 28-year-old German-Russian man stood to cash in through a fixed-price sale of 15,000 shares if the club's financial standing suffered through tragedy, they alleged.

He is said to have taken out a five-figure loan to bet on a stock drop for the football team.

"A significant share price drop could have been expected if a player had been seriously injured or even killed as a result of the attack," prosecutors said.

Ralf Jaeger, the top security official in North Rhine-Westphalia state, said the suspect had hoped to earn millions.

"The man appears to have wanted to commit murder out of greed," he added.

Dortmund player Marc Bartra broke a wrist in the explosion. Credit: PA

Officials said the suspect, identified as Sergej W, was arrested on Friday in the Tuebingen area in relation to the bus bombing on April 11, which caused minor injuries to Dortmund player Marc Bartra and left a policeman in shock.

Prosecutors said the suspect booked into the team's hotel in Dortmund and placed three explosives, packed with shrapnel, along the route the bus would take to reach the stadium for a Champions League match with AS Monaco.

"The explosive devices were detonated at the optimum time," they said, noting that the team bus was equipped only with security glass and not reinforced glass.

No one else is believed to be involved with the incident.

The club has thanked authorities in a statement on Facebook: "The fact that no further people were injured or killed was, as we now know, purely a matter of luck."

Captain Marcel Schmelzer said the team hopes to learn further details about the background to the attack.

He added: "This information is important to everyone who sat in the bus because it would make it significantly easier to process (what happened)."