LITTLE ROCK, Ark. — A judge peeled back the veil on a part of Arkansas’ highly secret execution procedure Thursday, saying prison officials must disclose more information about the lethal drugs they plan to use as part of an accelerated timetable of putting inmates to death next month.

Pulaski County Circuit Judge Wendell Griffen said packing slips that accompanied 100 vials of recently acquired potassium chloride must be released to prove they meet purity standards. The state Department of Correction said its word was good enough.

‘‘Just because you say it, doesn’t make it so,’’ Griffen told assistant attorney general Colin Jorgensen. ‘‘The department should have no problem disclosing that proof.’’

At 5:01 p.m., the judge gave the prisons department a half-hour to turn over the leaflets, saying the agency has known for a week, through Steven Shults’ lawsuit, that there was a demand for the material.

The prison officials, who plan to execute eight inmates in a 10-day period next month before one of the state’s lethal drugs expires April 30, have refused to release packing slips that detail how the drugs are to be used. The Associated Press has previously used the labels to identify drugmakers whose products would be used in executions against their will.

The prison system said its suppliers need anonymity to take part in executions and fears that releasing the labels will identify the state’s supplier. Griffen found that state confidentiality laws don’t apply to pharmaceutical companies that merely produce drugs.

Associated Press