LOS ANGELES (AP) _ Friends and relatives of Rick Nelson have denied reports that the singer was a drug abuser but in papers filed in a 1981 divorce action, his former wife said he '''constantly takes cocaine, Quaaludes and many other drugs.''

The issue of Nelson and drugs arose Wednesday when The Washington Post quoted federal investigators as saying the New Year's Eve airplane crash that killed the singer, his fiancee and five others may have resulted from a cabin fire ignited by ''free-basing'' cocaine.

The Post quoted unidentified sources as saying preliminary reports indicate Nelson's body contained a measurable level of cocaine not absorbed into his system when he died.

Nelson's friends and manager denied he had been a cocaine user and specifically that he indulged in free-basing, in which cocaine is mixed with solvents to purify the drug, which is allowed to dry and then smoked.

''It is all totally 100 percent false,'' Barbra Reinecke, the Nelson family's attorney, said Thursday. ''It's somebody's malicious attempt to blacken his image.''

The documents filed by Kristin Harmon Nelson's attorney during divorce proceedings said Nelson often held parties at his home where drugs were taken.

The divorce documents indicate Nelson's wife worried about the safety of the couple's four children.

Robert J. Nachshin of Los Angeles, who represented Mrs. Nelson, refused to discuss the case Thursday.

Mrs. Nelson filed for divorce in 1977. It was granted in 1981 and ended the 18-year-marriage.

Federal officials say they have yet to determine why the DC-3 crashed in Texas as Nelson and his band traveled from Alabama to a concert in Dallas. The pilot and co-pilot survived.

Autopsies determined that Nelson, 45, his 27-year-old fiancee, Helen Blair, four band members and a sound man died of smoke inhalation and burns.

The National Transportation Safety Board has not received any toxicological reports on the victims, which would indicate the presence of drugs or alcohol, said NTSB spokesman Ira Furman.

Nelson's friends denied the free-basing reports. Lynn Upton, wife of former Nelson band member Pat Upton, said she and her husband never saw Nelson use drugs. Nelson's manager, Greg McDonald, vehemently denied the Post story, saying Nelson and his fiancee were asleep when the fire broke out, and David Nelson said his younger brother did not use cocaine.

Nelson became known to millions of Americans as a youngster on his family's television show the ''Adventures of Ozzie and Harriet.''