By Aditya Kalra

NEW DELHI, Nov 12 (Reuters) - India's antitrust watchdog

has conducted nationwide raids at six paper mills in an

investigation of alleged price collusion in supplying paper to a

government school education body, two people with direct

knowledge said on Wednesday.

India's paper industry accounts for about 5% of the world's

production, and has an estimated annual turnover of $11 billion,

according to the Indian Paper Manufacturers Association.

The Competition Commission of India (CCI) has been

conducting surprise raids starting Tuesday in the states of

Maharashtra in the west and Punjab, Uttar Pradesh and New Delhi

in the north, said the sources, who declined to be named as the

matter is confidential.

The sources said the offices of Satia Industries,

Silverton Pulp and Chadha Papers were among those

raided. One of the sources said Shreyans Industries'

office was also being searched.

The sources did not name any of the other companies.

Satia Industries chief financial officer Rachit Nagpal

confirmed the CCI raids to Reuters during a telephone call,

adding the company had cooperated with investigators.

An official at Silverton Pulp declined to comment. Chadha

Papers and Shreyans Industries did not immediately respond to

Reuters queries.

The CCI does not make public any details of its cases of

alleged cartelisation or raids, and keeps the entire process

confidential. The watchdog did not respond to Reuters queries.

The case of alleged collusion was triggered last year

following a complaint by the government's National Council of

Educational Research and Training, which procures paper from

mills to make textbooks and other teaching material for schools.

The Council did not respond to a request for comment.

The raids come after another high-profile case triggered a

similar operation in March and targeted global advertising

agencies like GroupM, Interpublic, Publicis

and Dentsu ( DNTUF ) for alleged collusion over prices. The

investigation is ongoing, and will take several months.

The case was started after Dentsu ( DNTUF ) itself reported the

alleged collusion to the CCI, and later told Reuters it

had implemented stricter audits and controls. The other

companies have not commented on the allegations.

Officers typically seize documents and mobile phone data and

interrogate officials during such raids.