William Dalambert, 58, was charged with driving while impaired when police said he failed a sobriety test following the crash, which injured more than a dozen people. He passed a Breathalyzer test but authorities believed he was high on illicit or prescription drugs.
Dalambert consented to blood and urine tests. Preliminary tests came back negative for alcohol and drugs, officials said.
The Manhattan district attorney's office "is deferring any decision to prosecute until we have completed our investigation," spokeswoman Joan Vollero said in a statement.
Prosecutors are waiting for the full toxicology report, Vollero said.
"We are taking this matter seriously and prosecutors in the Office's Vehicular Crimes Unit are conducting a thorough investigation," she said.
Dalambert reportedly had 11 prior license suspensions on his record. After walking out of court late Wednesday night, Dalambert maintained his innocence in the crash.