SECURITY authorities have examined 1,000 pieces of evidence seized from an alleged bomb-making factory in Salmabad.
Three more suspects wanted for questioning have also been identified, said Public Security Chief Major-General Tariq Al Hassan.
They were named as Hussain Al A'ali (arrested), Ahmed Jaffar (at large) and Mohammed Yousif Mohammed Al Mughni (arrested).
Forensic experts from London's Metropolitan Police were earlier flown in to assist an investigation after the seizure of explosive materials during a series of raids last month.
"There is no timeframe for this investigation because this terrorist plan aimed to cause a massacre in Bahrain and all aspects related to it are being studied with the help of UK investigators," said Maj-Gen Al Hassan.
"Five tonnes of materials used in making bombs and 110 litres of chemicals that were seized in the operation last month are being studied at the forensic laboratory.
"The materials represent a serious threat to lives as they were stored in a residential area near a Ma'atam."
Maj-Gen Al Hassan said as part of the investigation police inspected 14 locations and raided several after completing legal procedures.
He said some of these searches were conducted late at night or early in the morning. Some residents were upset and in some cases made allegations of improper police procedure. Opposition groups have also alleged serious police misconduct, including thefts of large sums of money.
The minister takes these allegations seriously and while having full confidence that investigators conducted themselves properly, understands that an individual officer might have acted in an inappropriate way, he said.
"Families of the suspects were informed about the case and they showed no co-operation with security forces," he said.
"We have examined the confessions of the accused arrested in the case."
Three suspects had earlier been identified as Radhi Ali Radhi Abdulrasool, Jaffar Hussain Mohammed Yousif Eid and Dhafir Saleh Ali Saleh, two of them still on the run.
Maj-Gen Al Hassan said the suspects appeared to be part of a sophisticated operation.
"They were trained as they are using mobiles, fire extinguishers and other homemade explosives to cause harm," he said.
"But whether a foreign element is involved or who is behind it is still being investigated and any further details if revealed could hinder the investigation process."
Maj-Gen Al Hassan said police were still discovering bomb-making factories.
"At the moment, except the Salmabad illegal factory there is no other high-end bomb-making location," he said.
"But we are constantly discovering low-end factories where pipe bombs, fire extinguishers and other materials are hidden aiming to cause harm.
"There are many places and we are now tracking them down."