A few hours before the September 11, 2001, terrorist attacks in the United States, four petty thieves - Hakleen, Rajesh, Ghansu and Birju - were on the prowl on Platform II of the Hazrat Nizamuddin Railway Station in New Delhi.

The station is named after a 14th century Sufi saint and is a stone's throw away from his shrine. The area, frequented by drug addicts and homeless people, is known for petty crimes.

The four came here everyday and returned home with items like purses, gold earrings, parcels, or whatever came their way.

But that pleasant September day was special for the thieves, who had so far satisfied themselves with small loot.

The Gwalior-Nizamuddin Taj Express, which had arrived in the morning, had brought three huge, white packets, which were lying unattended on the platform.

There were a lot of people there, but none of them paid any attention to the packets. The four comrades kept an eye on the goodies, brought by Elbee, a private courier company, and waited for the crowd to thin down.

There was a passenger train on the adjacent platform. Around afternoon, the four hurriedly loaded all the three packets on the train and waited for it to move. And as luck would have it, the train did.

The four got into the train and stood at a distance from the packets.

Around a kilometre away from the station, the thieves threw the packets into nearby bushes and jumped out of the train.

Hakleen took the heist to his one-room government house in Janata Colony, Turkman Gate. The colony, where houses are given at subsidised rates, is meant for poor people.

All the four were baffled when they opened the packets one by one.

"They apparently didn't know what they had brought. But they were sure they had got something big," Deputy Commissioner of Police Deepender Pathak, who investigated the crime, told rediff.com.

"The total cost of the goods in the packets was estimated to be around Rs 2.2 crore (Rs 22 million)."

The young thieves had absolutely no clue that they had managed to secure accessories of the Indian Air Force's Mirage 2000 aircraft.

There was a brake parachute worth Rs 75 lakh (Rs7.5 million), a self-regulating pump, a symbol-generating unit, an oxygen failure detector, an auto-pellet and switching boxes.

The accessories were imported from France and had been stored at the Gwalior air force station. The packets were brought to Delhi so that they could be airlifted to the Hindustan Aeronautics Limited facility in Bangalore.

The railway police conducted preliminary investigations, but failed to find the goods. After three months, they finally lodged a complaint at the Nizamuddin Police Station. The case was later handed over to the Crime Branch.

It was a matter of national security. The Delhi police, the Intelligence Bureau and Research and Analysis Wing are jointly investigating the case now.

"There could be a larger angle to it and some international agencies could be involved," a senior police officer said.

Hakleen was arrested on Thursday after the police got a tip-off that there was something of 'national importance' in his house.

Later, the police also arrested Rajesh and Ghansu, who lived in a shantytown along the Yamuna River near the Red Fort.

The three led the cops to Birju, who was imprisoned in Tihar Jail in connection with a robbery.

Hakleen had managed to sell everything except the parachute.

The police are now looking for Hakleen's neighbour, a scrap dealer who allegedly bought the stolen goods.

The accessories had no general use and could be used only in fighter planes.

"They broke the accessories, siphoned off copper and other such material and sold them in pieces," Pathak said.

"They didn't know what to do with the brake parachute. It's a huge parachute, larger than the normal one. It is fixed at the tail of the fighter plane and opens at the time of landing. It helps to slow down the plane."

Even as the police claimed to have solved the two-year-old case, questions have been raised about the vigilance at railway stations.

Several small goods go missing from stations every day, but the cases are seldom solved.

More reports from Delhi