Liberian leader Ellen Johnson Sirleaf has welcomed the arrest of six people, including policeman Perry Dolo, for allegedly smuggling marijuana worth $4m (£2.5m) from Sierra Leone into Liberia.
Drug traffickers needed to face justice, the president's office said.
However, it denied an earlier police statement that Mr Dolo headed the presidential motorcade and had used the lead escort vehicle to allegedly transport 297kg (654lb) of marijuana.
Mr Dolo has not yet commented.
On Monday, Liberia's Drug Enforcement Agency (DEA) said Mr Dolo had been caught with three other people while travelling in "Escort 1".
"We want to speedily send them to court... because the case is too high. Using a presidential car? It's too big," DEA head Anthony Souh said.
In a later statement, Ms Johnson's office said the escort vehicle had been "decommissioned" and returned to the police two years.
It confirmed that Mr Dolo was a policeman but denied he was commander of the presidential motorcade.
"The presidential motorcade is a combination of the various security vehicles, which is headed by the Executive Protective Service," the statement said.
It added that Mr Dolo had been arrested with five other people - another Liberian policeman, a Sierra Leonean military officer, a businessman, a taxi driver, and a former member of the armed forces.
Security sources at the Bo-Waterside border crossing said Mr Dolo had been under surveillance for two weeks before he was apprehended at the weekend in the town of Tienne, about 20km (12 miles) inside Liberia and 120km west of the capital, Monrovia.
Ms Sirleaf was satisfied with the "swift action" of the security forces, and had instructed them to increase their vigilance to curb the illegal drug trade, her office said.
The BBC's Jonathan Paye-Layleh in Monrovia says Liberia's DEA has in recent years stepped up efforts to curb marijuana farming in Liberia's countryside, but they often complain of a lack of resources.
According to the 2012 UN Office on Drugs and Crime report, 9% of Liberian high school students use the drug.
Liberia is recovering from a brutal civil war that ended about a decade ago.