The Central Forensic Science Laboratory is conducting "mass spectro-photometric tests" on the clothes of Rahul Mahajan and Pramod Mahajan's late secretary Vivek Maitra to analyse whether they had any stains of heroin or cocaine.

• Rahul Mahajan Case

While maintaining that these tests would be only "qualitative" and not "quantitative", senior CFSL officials said the clothes were being passed through photometric rays to analyse the stains on them.

Under this test, every chemical or fabric gives off a different colour spectrum by which CFSL will be able to analyse stains on the clothes.

The CFSL officials, however, said the tests could only help in ascertaining the material that had caused the stains and not the quantity, a mystery which has put Delhi [Images] police on the defensive.

Two cloth pieces were among the first five samples sent in by Delhi police to CFSL on June 3 for conducting tests.

Other samples handed over by Delhi Police to CFSL on that day included a one inch by one-and-a-half inch red pouch and stomach wash of Rahul and Maitra collected from Apollo Hospital and AIIMS.

Delhi police sent another batch of six samples to CFSL on June 6, including Rahul's gastric lavage, two bottles of champagne consumed at a party at Pramod Mahajan's house on the night of June 1, half-filled water bottles, empty glasses and a tinned dry fruits box.

However, the powder found in the house was not among the items sent for examination.

Maitra died following the June 1 party while Rahul was arrested for alleged drug abuse.