Jay McMullen, an award-winning CBS television journalist who helped establish modern newsgathering techniques through his early use of the hidden camera, died March 10 at a hospice in Greenwich, Conn. He was 90.

He had a pulmonary embolism, said his daughter Anne McMullen.

Mr. McMullen got his start as a radio broadcaster on the front lines during World War II and joined CBS in 1949. Decades before cable and satellite programming fragmented the TV market, millions of Americans watched his investigations on the network’s documentary unit, called “CBS Reports,” and on the evening news hosted by Walter Cronkite.

Mr. McMullen’s subjects included organized crime, drug trafficking and urban poverty. Concealed, specialized camera equipment figured prominently in his most noted work, the 1961 documentary “Biography of a Bookie Joint,” which was narrated by Cronkite and produced by Fred W. Friendly, who later headed CBS News.

Mr. McMullen’s months-long investigation exposed the workings of an illegal Boston gambling operation, including its patronage by city police officers, and incited a wave of national outrage.

Jay McMullen (shown in 1968) helped establish modern newsgathering techniques through his use of hidden cameras. (CBS News )

He obtained some of his most incriminating footage by hiding an 8mm film camera in a lunchbox and toting it into the gambling parlor, where he placed bets. Undercover reporting was another hallmark of his career. He won an Emmy Award for his 1972 report “The Mexican Connection,” in which he detailed the activities of the cross-border drug trade by moving to Mexico for eight months and posing as a drug buyer.

Over the years, Mr. McMullen’s reporting practices became mainstays of tabloid shows and mainstream television programs such as CBS’s “60 Minutes” and ABC’s “Primetime Live.”

The techniques have been criticized as invasive and sensationalistic, and Mr. McMullen said he did not relish the need to “sneak around.” But he said that sometimes — as in the case of the Boston bookie joint — there was no other way to get the story.

Moreover, hidden cameras allowed Mr. McMullen to “bring visual evidence to the reportage,” said Robert Thompson, a professor of television and popular culture at Syracuse University.

“Biography of a Bookie Joint” was a critical and popular success, and a Washington Post review by Lawrence Laurent said it demonstrated how the small-time gambler who handed his $2 to an illegal bookie was helping to finance the underworld.

Mr. McMullen said he regarded journalism as public service. He moved into a Chicago slum for his 1967 report “The Tenement” and followed the drug route from Turkey through Syria, into Italy and finally to the streets of Harlem for “The Business of Heroin” (1964). In what was regarded as groundbreaking work, he filmed drug pushers through the back window of a truck.

His other significant documentaries included “The Baby Makers,” a 1979 report about artificial insemination, and “The Toyota Invasion” (1981), about the rise of Japanese automakers and the demise of Detroit’s car manufacturers.

By the mid-1980s, the New York Times was reporting the “near extinction” of in-depth TV documentaries as television “newsmagazine” shows gained popularity. In 1983, Mr. McMullen produced one of his final works, a widely watched program called “After All Those Years.” It was about employers who replaced veteran workers with cheaper labor.

“Am I writing my own epitaph?” Mr. McMullen said. “Can I divorce myself from the feeling of getting dumped? I think that’s a cloud that hangs over everybody’s head.” He retired two years after the show aired.

Jay Latimer McMullen was born April 8, 1921, in Minneapolis and raised in Cleveland.

During World War II, he was a volunteer ambulance driver, was attached to the French Foreign Legion in the Middle East and then served in the U.S. Army. While in uniform, he was a correspondent for NBC Radio. His decorations included the Bronze Star Medal, according to CBS.

After receiving a bachelor’s degree in political science from Columbia University in 1948, he joined CBS as a writer for the public affairs TV program “Vanity Fair.” His early radio work included “Babies, C.O.D.,” a 1954 report about adoption, and “Who Killed Michael Farmer” (1958), a study of juvenile crime, which won the prestigious George Polk Award.

Survivors include his wife of 58 years, the former Diane Fryburg, of Greenwich; two daughters, Anne McMullen of Olympia, Wash., and Diana Lepis of Stamford, Conn.; and three grandchildren.

“I enjoyed my work,” Mr. McMullen once told an interviewer. “I believed that what I was doing was important. . . . I ended up writing, narrating, reporting — in other words, having complete control over the broadcasts I did. For a journalist, that’s great.”