A reward of $30 million is being offered for information and evidence leading to the culprits behind the downing of Malaysia Airlines Flight MH17 in eastern Ukraine, CTV reported. The "most likely" scenario is that Flight MH17 was shot down from the ground, chief Dutch prosecutor overseeing the criminal investigation said last week.

A German fraud investigation company, Wifka, was offered the money by an anonymous client to look into the July 17 attack which brought down the Boeing 777, they said in a statement Friday.

The plane, heading to Kuala Lumpur from Amsterdam, went down over territory held by pro-Russian rebels. All 298 passengers and crew on board were killed.

The clients, requesting anonymity, have payed the private investigators to find out who shot down the plane, who gave the order, who covered it up and what happened to the weapon used.

The reward money for "information and evidence" is "securely deposited" in Zurich, Switzerland, and will be paid out there or "in a different neutral place of the whistle-blower's choice," according to the firm's statement.

Additionally, whistle-blowers would be offered new identities, with Wifka vowing not to identify them in any manner. They also advised would-be whistle-blowers "to take great care" and contact them through a lawyer, adding: "Details should not lightly be given away in emails or on the phone." 

Josef Resch, who runs Wifka, told NBC News on Wednesday that the offer was genuine and that the investigation was in full swing.

Although Resch had not fully been aware of his clients' identities earlier, he had held several meetings about the case in different countries, with one of the middlemen allegedly having a Swiss accent, he told German financial magazine Capital.

He also "offered different theories about who his clients might be, including the possibility of mega-rich Russians trying to hurt President Vladimir Putin's reputation," according to NBC News. "Their offer was credible, he said, because the company had already received a fee of 40,000 euro (around $51,000)."

A fee of 500,000 euro ($647,000) has been promised if the investigation proves to be successful, Capital magazine added.