The 22 September deployment was watched with anxiety in some circles
Syria has reportedly moved more troops to its side of the eastern Lebanese border, weeks after boosting numbers along Lebanon's northern frontier.
Reports said the troops had dug trenches and set up checkpoints in the northern Bekaa valley region.
The Syrian authorities have not commented on the latest deployment.
Damascus said earlier troop movements were aimed at combating smugglers. On Monday, the US warned Syria against a possible intervention in Lebanon.
Anti-Syrian Lebanese groups fear Damascus might use insecurity in northern Lebanon as a pretext for a military intervention.
The Lebanese army says about 10,000 Syrian forces have been deployed on the border since 22 September when the first units moved in.
Syria was the main power broker in Lebanon after the 1975-90 civil war but withdrew tens of thousands of troops from the country after popular pressure from opponents in Lebanon in 2005.
It says measures taken along the border are in line with agreements between Lebanon and Syria, which have been trying to normalise relations with support from France.
In recent days, the US has established a bilateral military commission with Lebanon, aimed at building up the country's armed forces.