"I do not see it as a setback as our case is still under investigation," said the country's Internal Security Secretary, U.K. Bansal, referring to Tahawwur Hussain Rana's acquittal in a Chicago court.

Rana was accused of allowing his immigration business to be used as cover for his friend David Coleman Headley to scout out potential targets in India's financial and entertainment capital before the attacks.

Headley testified against him but a jury on Thursday found there was insufficient evidence to convict.

Federal investigators are preparing a case against both Rana and Headley, with a view to trying them in India, Bansal told reporters in New Delhi.

"When the probe is over, we will produce the evidence in the court," he said, according to the Press Trust of India news agency.

A total of 166 people were killed and more than 300 wounded when 10 heavily-armed gunman belonging to the banned, Pakistan-based group Lashkar-e-Taiba (LeT) stormed Mumbai on Nov. 26, 2008.

The sole surviving gunman, Pakistani national Ajmal Amir Qasab, was convicted of "waging war" against India, murder, attempted murder and terrorism offenses at a trial in Mumbai last year and sentenced to death.

Two Indian nationals who were on trial alongside him were acquitted of providing information to the attackers about targets, with their defense teams insisting that it was Headley who provided reconnaissance details.

But the trial judge ruled that implicating Headley was not admissible.

Rana still faces up to 30 years in jail, as the Chicago jury convicted him of helping the LeT to plan an attack on a Danish newspaper for publishing cartoons of the Prophet Muhammad (pbuh).

Headley was arrested in 2009 and has admitted 12 terror charges after prosecutors agreed not seek the death penalty or allow him to be extradited to either India, Pakistan or Denmark to face related charges.

In a mixed verdict, the jury also found Rana, 50, a former Pakistan Army doctor with Canadian citizenship, guilty of conspiring to attack a Danish newspaper, a plot hatched by the militant group but never carried out.

In the trial, held in US federal court in Chicago, the key witness — Rana's childhood friend, Headley — implicated Pakistan's intelligence agency, ISI, in the Mumbai attacks.

Headley admitted scouting targets for the Mumbai attackers sent by Lashkar-e-Taiba. The judge gave both sides 60 days to file post-trial motions and did not set a sentencing date. Rana faces a maximum of 15 years in prison for each of the two counts.

US Justice Department officials said the case was not over. "I'm hoping there are other defendants ... that other people are brought to justice, both here and overseas," said Patrick Fitzgerald, the US Attorney in Chicago who has led prosecutions of several militants.

Fitzgerald would not say what steps might be taken to track down the six Pakistanis charged in the US case, including Headley's main contact with the ISI, known only as Maj. Iqbal. None is in custody.

The case revealed contacts between ISI and militants who are fighting India over the disputed territory of Kashmir. Headley testified that other ISI officers were helpful to him and trained him in spycraft, but that he suspected ISI "higher-ups" did not know of the Mumbai plot. Rana, 50, was charged with supporting the plots to attack Mumbai and Denmark, and of supporting Lashkar-e-Taiba.

He was found guilty of supporting the Danish plot and Lashkar, but the jury did not find his support of Lashkar resulted in any deaths, sparing him a life prison sentence.

"We think they got it wrong," Rana's lawyer, Patrick Blegen, said of the guilty verdicts, adding he planned to appeal.

"He faces 30 years for basically buying a plane ticket," defense lawyer Charles Swift said, referring to Rana arranging one of Headley's tickets to Denmark to perform reconnaissance work on the Jyllands-Posten newspaper.