Eleven of 23 city stores surveyed in the last two days by the D.C. Office of Consumer Protection were found selling children's sleepwear treated with potential cancer-causing chemical Tris, more than two weeks after such sales were banned by the federal government.

Four stores had removed all Tris-treated clothing from their shelves since the April 8 ban, according to the survey, and another eight stores were still selling garments made of 100 per cent polyester, where there is some question about whether they have been Tris-treated.

Several store managers said while 100 per cent polyester has been treated with Tris in the past, spring shipments do not contain the chemical.

Edith Barksdale-Sloan, director of the consumer protection office, personally headed the 20-member survey team to determine if merchants were complying with the ban imposed by the federal Consumer Product Safety Commission on the sale of garments treated with Tris, a flame-retardant.

Stores where the Tris-treated garments were found will be revisited, Sloan said. If any Tris-treated clothes are found, a cease and desist order will be issued against the stores, she said.

"It (the survey) has shown us that the ban has not been adhered to, that . . . the stores continue to carry the Tris-contaminated garments of acetate and triacetate," she said yesterday afternoon after returning from a second-day of surveying downtown Washington stores. "We're going to have to go back," she said.

The ban applies to an estimated 13 million sets of size 0 to 14 pajamas and other sleepwear for children. All acetate or triacetate blends used in making children's wear have been treated with Tris, according to the U.S. commission. These fabrics were treated with Tris after the 1972 Flammable Standards Act required that all children's sleepwear be fire-resistant.

Labels on sleepwear do not specify the presence of the chemical, which is believed to cause kidney cancer in humans. Consumers can attempt to determine the presence of Tris only of knowing what fabric was used in making the sleepwear, Sloan said.

The federal commission said the following fibers are "inherently flame-resistant" and therefore completely free of Tris: modacrylic (sold as verel, and SEF), modacrylic blends, matric fibers such as Cordelan, matric blends, vinyong (Leavil) and vinyon blends.

Sleepwear made of 100 per cent cotton also are Tris-free but contain two other flame-resistant chemicals that are not under study for possible cancer causing properties, Sloan said. Garments made of 100 per cent nylon are also Tris-free, she said.

Since some sleepwear articles for children made of 100 per cent polyester contains Tris and others do not, Sloan purchased some at general stores and said she would have them analyzed by a laboratory.

Store officials at Hecht's and at Garfinckel's downtown, two of the nine stores where the surveyers found sleepwear made of the 100 per cent polyester, told the surveyers that manufacturers had assured them taht the garments were from their spring stock and were thus Tris-free.

The Carter manufacturing company, a large maker of children's clothing, has told retail stores in writing that as of Feb. 12, it discontinued the shipment of all merchandise made with Tris-treated fabrics. To insure there is no confusion because of shipping dates, Carter's also has sent stores a list of style numbers, stating which are Tris-treated and which are not.

Managers at all the stores with Tris-suspected clothing said they would remove the garments from sale and seveal managers removed the merchandise in the presence of the surveyors.

Several managers also said they had previously removed some Tris-treated garments and did not realize that those found by the surveyors also contained the banned chemical.

Most stores said they would give customers refunds for returned Tris-treated garments, both used and un-used. Some stores said they would require proof of purchase from that store.